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By William Peters, M.D., Ph.D.

02/25/2019

The Use of Tamoxifen for Early Types of Breast Cancer

Breast cancer can develop in different parts of the breast, with most beginning in the ducts that carry milk to the nipple. The earliest form of breast cancer is ductal carcinoma in situ (DCIS), in which cells that line the milk ducts of the breast have become cancerous but have not spread into the surrounding breast tissue.  Standard treatments for DCIS include surgery, either lumpectomy or mastectomy, radiation therapy, and if the DCIS tissue is positive for hormone receptors, hormonal therapy for five years with either tamoxifen or aromatase inhibitors, such as anastrazole or letrozole. 

Recently, a practice changing randomized study called TAM-01 showed that tamoxifen at one quarter of the standard dose and for a much shorter time in comparison to a full dose of tamoxifen can equally reduce the risk of cancer recurrence and significantly reduce the risk of side effects. Tamoxifen is a drug that is been available since the early 1970s and was primarily studied and developed in patients with more advanced breast cancer. The side effects associated with the current standard dose of 20 mg per day include bone and muscle aches, hot flashes, vaginal dryness, and painful intercourse, as well as a low but real increase risk of endometrial cancer and of blood clotting.

This new study began over a decade ago and stemmed from small clinical observations that showed lower doses of tamoxifen appearing as effective as higher dose treatments. In the study, women under the age of 75 with early forms of breast cancer were randomly assigned to receive either tamoxifen at five mg a day or placebo for three years.  Most of the patients in the study had estrogen receptor positive DCIS (70%), but the study also included other patients with atypical ductal carcinoma (ADH) and lobular carcinoma in situ (LCIS). The patient demographics in each group were very similar.

The results showed after a follow-up of five years:

  • 97% of the patients were alive.
  • Breast cancer had recurred in 5% of the women receiving tamoxifen.
  • Breast cancer had recurred in 11% of the women in the placebo group. 
  • This showed a statistically significant and clinically meaningful result of more than a 50% reduction in the risk of disease recurrence.
  • The risk for developing breast cancer in the other breast was 75% less for patients receiving tamoxifen compared with those getting placebo.

Importantly, the incidence of serious side effects was less than 1% in each group. There were slightly more daily hot flashes in those receiving tamoxifen, but their intensity was less. Also, there were no significant differences in the frequency of vaginal dryness/pain and musculoskeletal pain between tamoxifen and placebo. Altogether, these results show a benefit for tamoxifen in one of every 22 patients treated for three years and occurrence of side effects in only one of every 218 patients, giving a tenfold benefit to risk ratio.

This study represents a real step forward for breast cancer patients, by being able to achieve the same benefit with the lower dose, shorter duration, and fewer side effects treatment in comparison to the higher dose treatment. Although the results are only present in the earliest forms of breast cancer, there is reason to hope that they can be extended to other more invasive types of breast cancer.

For any questions or concerns, please contact Dr. Peters at (904) 277-2700.

 

This article is linked here for your convenience: http://cancerres.aacrjournals.org/content/79/4_Supplement/GS3-01.

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